1. Field of the Invention
The present invention relates to the treatment of correction of design pattern data for fabrication of photomask, which is needed following the miniaturization and high density of patterns on a semiconductor wafer, and in particular relates to a method for correcting design pattern data used for forming a pattern of photomask so as to obtain the objective shape of a figure pattern on a wafer and a photomask having patterns corrected by the method for correcting design pattern data.
2. Related Art
Recently, improved integration and functionality have been desired for various LSIs typified by ASIC. Namely, it is desired to decrease chip size as much as possible to realize high functionality.
The above-mentioned LSIs such as ASIC are produced through several steps of making figure data which are called xe2x80x9cpattern dataxe2x80x9d for forming patterns of a photomask through function design, logical design, circuit design and layout design and others, fabricating a photomask using the figure data, and thereafter transferring the patterns of photomask on a wafer by demagnification projection to carry out the fabrication of a semiconductor circuit.
A photomask is produced generally by drawing the above-mentioned figure data (pattern data) on photosensitive resist put on a shielding film of a substrate for photomask (also called xe2x80x9cphotomask blanksxe2x80x9d) using an electron beam exposure system or aligner of photo such as excimer laser, and through the steps of development and etching.
Namely, photosensitive resist is applied on a shielding metallic thin film provided on a glass substrate and dried. A latent image is formed on the photosensitive resist by applying ionizing radiation only to the fixed,areas, and the photosensitive resist is developed to obtain the resist patterns having a desired shape corresponding to the exposure areas of ionizing radiation. Thereafter, the metallic thin film is etched into the shape of the resist pattern by using the resist pattern as etching resistant resist, by which a photomask having a desired metallic thin film is formed.
In the case where patterns of photomask are exposed onto a wafer by demagnification projection to transfer the patterns to the wafer, the photomask is also called xe2x80x9creticle maskxe2x80x9d.
In such a way, patterns of photomask are transferred onto a wafer by demagnification projection by which circuit patterns are formed on a wafer. However, there is a case where patterns are not formed onto a wafer with the same size as the patterns of photomask according to the design conditions because together with LSI being more integrated, recently the size of the exposed shape (size of the exposed shape on a wafer) has miniaturized more and more to the extent that the size of the exposed shape approaches the wavelength of an exposed beam or the size of an exposed shape is smaller than the wavelength of the exposed beam so that transformation of the shape of exposed beam called xe2x80x9coptical proximity effectxe2x80x9d is generated when transferring patterns of photomask on a wafer through demagnification projection. Accordingly, there is a case where even if patterns formed on a photomask have the same size, patterns corresponding to the patterns formed on the photomask are not formed on a semiconductor wafer with the same size as the size of patterns of the photomask according to design conditions.
In such a way, a difference between figure patterns of the photomask and the patterns formed on a wafer corresponding to the figure patterns of the photomask are produced. Therefore, it is necessary to change the shape of the photomask according to the objective shape of the figures formed on the wafer.
Thus it is now necessary to use figure data in which correction is given to original figure data (hereinafter it is called xe2x80x9cdesign pattern dataxe2x80x9d) for the fabrication of the photomask.
Further, a difference between figure data used and figures on a photomask corresponding to the figure data has started to be problematic.
In such a way, the correction of design pattern data in the formation of fine patterns on a semiconductor wafer and the correction of design pattern data in the fabrication of photomask came to be applied.
First, referring to drawings, the technique of correction of design pattern data in the formation of fine patterns on a semiconductor wafer is explained concretely.
FIG. 3(a) shows design pattern data. FIG. 3(b) shows an example of patterns formed on a semiconductor wafer in case of the size of the design pattern being smaller than the wavelength of a light source of aligner for production of a semiconductor.
This shows that a difference in angles and width of line of design patterns appears according to the phenomenon of optical diffraction.
The technique of lessening the difference has been carried out actively from the latter half of the 1990""s.
FIG. 6(a) shows corrected pattern data in which correction is given to design patterns applied until now. The correction shown in FIG. 6(a) is for the design patterns shown in FIG. 3(a) to form a corrected design pattern.
The shapes of patterns formed on a semiconductor wafer become the shape close to a desired shape as design patterns formed on a wafer shown in FIG. 6(b), using the corrected design pattern data.
Further, when forming design patterns on a semiconductor wafer, deviation from the correct shape of patterns arise according to the position of the pattern within an individual chip as a unit of exposure of the semiconductor, due to a process of semiconductor.
FIG. 3(b) shows an example in which figure 153 becomes thinner by the influence of position.
As for the deviation from the correct shape of a pattern depending on the position of a pattern generated within a chip of a unit of exposure of the semiconductor, the correction of a design pattern is difficult. Therefore, the correction of a design pattern for controlling deviation is not applied according to a general rule.
Then, referring to drawing, the correction of a design pattern in the production of a photomask is explained.
FIG. 4(a) shows design pattern data. FIG. 4(b) shows the shape of figure patterns formed on a photomask corresponding to the design pattern data shown in FIG. 4(a).
Deviation of the roundness of the shape of the pattern formed on a photomask shown in FIG. 4(b) and deviation of the width of line of the pattern depend on arrangement of the design patterns and the steps of producing a photomask.
Accordingly, in order to make patterns formed on the photomask approach to the shape of design pattern, a use of corrected design pattern data corrected as shown in FIG. 7(a) was suggested.
FIG. 7(b) shows the shape of figure patterns formed on a photomask corresponding to the corrected design pattern.
Further, as shown in FIG. 4(b), there is the problem that a difference between pattern data and the shape of figure patterns formed on a photomask arises according to the position of a pattern within the photomask.
As for a difference between the pattern data and the shape of figure patterns depending on the position of the pattern within a photomask generated in the production of photomask, the correction of design pattern is difficult. Therefore, the correction of the design pattern for controlling the difference is not applied in a general rule.
The application of both the technique of correction of design pattern in the fabrication of a photomask and the technique of correction of design pattern in producing a semiconductor wafer is needed for obtaining both the shape of figure patterns of the photomask close to the objective shape of the pattern and the shape of figure patterns formed on a semiconductor wafer close to the objective shape of the pattern. However, heretofore, first, the correction of a design pattern for semiconductor wafer was applied, then, the correction of a design pattern for a photomask was carried out since the amounts of correction in a semiconductor wafer is larger than that for photomask in general.
An original design pattern is as shown in FIG. 8(a), the correction of design pattern for semiconductor wafer is as shown in FIG. 8(b) and the correction of design pattern for photomask is as shown in FIG. 8(c).
In this case, if original design pattern is assumed to be a rectangle as shown in FIG. 8(a), the correction of design pattern for a semiconductor wafer is made to form a figure having twenty edges as shown in FIG. 8(b), and the correction of design pattern for the photomask is made to be a figure having one hundred edges as shown in FIG. 8(c).
However, such a correction is not realistic. It can be imagined that an actual time to carry out the correction of the design pattern and the amounts of data generated after the correction of the design pattern becomes enormous. Further, there is no information on the technique of correction in which the correction of the design pattern for the semiconductor wafer is associated with the correction of design pattern for the photomask.
However today, patterns formed on semiconductor wafers are finer and finer and in case of the correction of a design pattern being carried out by the prior art, the above-mentioned two corrections become essential.
The necessity for consideration of a difference between original figure data and patterns formed on a photomask corresponding to the original data and a difference between the original figure data and patterns formed on a wafer corresponding to the original figure data appeared recently. Therefore, a practical application of the technique of correction was required in which the correction of design pattern data in the formation of fine patterns on a semiconductor wafer is associated with the correction of design pattern data in the fabrication of photomask.
According to this, it is an object of the present invention to provide a method for correcting design pattern data for semiconductor circuit in which recently, in the middle of miniaturization and the high density of mask patterns being developed, the technique of correction is applied at a practical level in which the correction of design pattern data in the formation of fine patterns on a semiconductor wafer is associated with the correction of design patterns in the fabrication of photomask.
Namely, it is an object of the present invention to provide a method for correcting design pattern data for a semiconductor circuit in which the process of correction is possible within a practical time without the amounts of data to be processed becoming enormous.
Further, it is another object of the present invention to provide a photomask and a method for inspecting thereof in which figure data (pattern data) is used so that the above-mentioned correction of data is given.
A method for correcting design pattern data of a semiconductor circuit of the present invention is a method for correcting design pattern data in the fabrication of semiconductor in which figure patterns are formed on a semiconductor wafer using design pattern data designed for the semiconductor circuit and transferring the figure pattern of a photomask from a photomask to a semiconductor wafer by exposure, characterized in that the method for correcting design pattern data of the semiconductor circuit comprises the steps of: (a) extracting a difference between particular pattern data and figure patterns formed on a semiconductor wafer, wherein said figure patterns corresponding to said pattern data comprised of test pattern data or said pattern data comprised of test pattern data and design pattern data are formed on said semiconductor wafer, using a photomask with the high fidelity in which there is a no or very small difference between pattern data and figure patterns of photomask, according to the specified method for fabricating a semiconductor and said figure patterns formed on a semiconductor wafer are measured by which a difference between said pattern data and said figure patterns of semiconductor wafer is extracted; (b) extracting a difference between said pattern data and figure patterns formed on a photomask, wherein said figure patterns corresponding to said pattern data is formed on the photomask according to the specified method for fabricating a photomask and said figure patterns formed on a photomask is measured by which a difference between said pattern data and said figure patterns formed on the photomask is extracted; (c) deriving the amounts of correction, wherein the amounts of correction to transform the shape of said pattern data is derived on the basis of the information on differences extracted from said step of extracting the difference between said pattern data and said figure patterns formed on a photomask and said step of extracting the difference between said pattern data and said figure patterns formed on a semiconductor wafer in such a manner that the difference between said pattern data and said figure patterns of semiconductor wafer becomes smaller; and (d) applying the correction, wherein the shape of design pattern data is corrected using the amounts of correction derived from the step of deriving the amounts of correction by which the corrected design pattern data is generated.
Or a method for correcting design pattern data of semiconductor circuit of the present invention is a method for correcting design pattern data in the fabrication of semiconductor in which figure patterns are formed on a semiconductor wafer using design pattern data designed for semiconductor circuit and transferring the figure pattern data from a photomask to a semiconductor wafer by exposure, characterized in that the method for correcting design pattern data comprises the steps of: (a) extracting a difference between particular pattern data and figure patterns formed on a semiconductor wafer, which corresponding to said pattern data comprised of test pattern data or said pattern data comprised of test pattern data and the design pattern data, are obtained by simulation on the assumption that photomask is fabricated in high fidelity to said pattern data; (b) extracting a difference between said pattern data and figure patterns formed on photomask, wherein figure patterns corresponding to said pattern data are formed on photomask using said pattern data and according to the specified method for fabricating photomask and said figure patterns formed on photomask is measured by which a difference between said pattern data and said figure patterns formed on the photomask is extracted; (c) deriving the amounts of correction, wherein the amounts of correction to transform the shape of said pattern data is derived on the basis of the information on differences extracted from said step of extracting a difference between said pattern data and said figure patterns formed on photomask and from the step of extracting a difference between said pattern data and said figure patterns formed on a semiconductor wafer in such a manner that a difference between said pattern data and said figure patterns of semiconductor wafer corresponding to said pattern data becomes smaller; and (d) applying the correction of design pattern data, wherein the shape of design pattern data is corrected using the amounts of correction derived from said step of deriving the amounts of correction by which the corrected design pattern data are generated.
A photomask of the present invention is characterized in that the photomask is fabricated using the corrected design pattern data formed in the step of applying the correction of design pattern data in any of the above-mentioned methods for correcting design pattern data.
A method for generating pattern data for the inspection of photomask in which the method is used for the inspection of photomask fabricated using the corrected design pattern data generated in the step of applying the correction of design pattern data mentioned in any of the above-mentioned method for correcting design pattern data, characterized in that the method for generating pattern data for the inspection of photomask comprises of the steps of: (e) extracting the amounts of transformation of photomask patterns, wherein the amounts of transformation of photomask patterns against pattern data are extracted from the information obtained from the step of extracting a difference between particular pattern data and figure patterns formed on photomask mentioned in any of the above-mentioned methods for correcting design pattern data; (f) forming transformed pattern data, wherein transformed design pattern data to which design pattern data is transformed against the corrected design pattern data generated in the step of applying correction of design pattern data mentioned in any of the above-mentioned methods for correcting design pattern data are generated on the basis of the amounts of transformation extracted in the step of extracting the amounts of transformation of photomask pattern; and (g) generating inspection data, wherein the inspection data for inspecting fabricated photomask are formed from transformed design pattern data generated in the step of forming transformed pattern data using the corrected design pattern data.
A method for inspecting a photomask of the present invention is characterized in that photomask fabricated using the corrected design pattern data generated in the step of correcting correction is inspected using the pattern data for inspection of photomask generated as above-mentioned, wherein the pattern data for inspection of photomask is compared with the formed patterns of photomask.
According to the above-mentioned constitution of invention, a method for correcting design pattern (data) of semiconductor circuit of the present invention enables the provision of a method for correcting design pattern data of semiconductor circuit, wherein recently, in the middle of miniaturization and high density of mask pattern being developed, the technique of correction is applied at a practical level in which the correction of design pattern data in the formation of fine patterns on a semiconductor wafer is associated with the correction of design patterns in the fabrication of photomask.
Namely, the present invention provides a method for correcting design pattern data of semiconductor circuit, wherein the process of correction is possible within practical time without the amounts of data to be processed being too enormous.
The details are as follows. In the present invention, the premise that ideal photomask with no difference between design pattern data generated by simulation and figure patterns formed on photomask is not made since a difference between design pattern data and figure patterns formed on semiconductor wafer is combined with a difference between design pattern data and figure patterns formed on photomask. Therefore, the load of production of photomask is decreased.
Further, the correction for fabricating ideal photomask is not needed. Therefore, the correction of design pattern data can be realized with the realistic amounts of data and within realistic time to treat the correction of design pattern data.
According to the above-mentioned constitution of invention, a method for generating pattern data for inspection of photomask of the present invention enables the provision of data for inspection of fabricated photomask, from the corrected design pattern data generated in a method for correcting design pattern data of semiconductor circuit of the above-mentioned present invention in which the correction of design pattern data is added. Finally, the fabrication of photomask and the process of inspection thereof can be established in which the objective figure patterns can be formed on semiconductor wafer faithfully to original design pattern data, by which the production of photomask is made at a practical level.